How can I close this?

 From:  Michael Gibson
9361.4 In reply to 9361.1 
Hi Lee, yes that helps a lot if you can post your .3dm model file instead of only a screenshot. That then allows a close examination of your geometry and also tests on it neither of which can be done on just a screenshot.

It sounds like you've got this all set up ok but the main way to handle a case like that is to make sure the main object you are working on is a closed solid.

When you do a boolean on a closed solid then the "side walls" of the cutting object will be automatically left behind and you then don't have to do any additional work to close up such things.

When your base object is not a solid then a boolean difference will only cut up surfaces and not be able to form a solid result automatically, like you are describing.

The booleans are mainly focused on working with solids, they use which solid volume a piece is in to determine which areas to keep and discard. If your base object is not a closed solid then there are no volumes to work with and the boolean will only work as a surface operation instead.

- Michael